1. Field of the Invention
The present invention relates to a method and apparatus for quenching tubulars and, more particularly, to a method and apparatus for simultaneously quenching the inside and outside surfaces of tubulars.
2. Prior Art
In order to produce the desired metallurgical properties in tubular goods, it is necessary to provide heat treatments which may include rapid quenching from elevated temperatures to below the lower critical temperature. Such quenching may be provided in various ways, including water spraying on the external surface of the tubular, water spraying on the internal surface of the tubular, dipping the tubular vertically into a quenching bath, simultaneous water spraying on both the external and internal surfaces of the tubular, or dipping the tubular laterally into a quenching bath.
Kuchera U.S. Pat. No. 3,252,695 discloses an apparatus for quenching channel members in which the channel is held in a horizontal position by movable die sections and quenched on its inside and outside surfaces along its length. The method of quenching is set forth in the contemporaneous Kuchera U.S. Pat. No. 3,294,597.
Winstrom U.S. Pat. No. 3,682,722 describes a method of quenching tubulars by suspending the tubular in a tower, heating the tubular and then lowering it into a pit between rotating inside and outside quenching heads.
Huseby U.S. Pat. No. 3,294,599 describes a method and apparatus by which tubulars are simultaneously quenched on the inside and the outside by passing the heated tubular in a horizontal direction between inside and outside quenching heads. The tubular is first heated in a horizontal furnace and then passed in a horizontal direction over one of two inside quenching heads mounted on quenching mandrels having a length sufficient to accommodate the length of the tubular. The outer quenching head is then indexed horizontally toward the furnace to clear the tubular, and the inside quenching assembly is then moved laterally so as to register the second inside quenching head with the horizontal furnace and outside quenching head thereby permitting the quenching of a second tubular while the first quenched tubular is removed from the apparatus. Huseby also discloses an alternative apparatus wherein a single outside and inside quenching assembly is mounted to swing in a horizontal plane to permit removal of the quenched tubular from the quenching mandrel.
Pope et al. U.S. Pat. No. 4,123,301 discloses another method and apparatus for providing simultaneous inside and outside quenching of tubulars. Pope discloses a fixed outside quenching head and an axially movable mandrel upon which is mounted an inside quenching head. The heated tubular is first passed over the inside quenching head when that head is in registry with the outside quenching head. Thereafter, the mandrel and inside quenching head are moved axially to clear the tubular and the tubular is transferred laterally to a conveyor leading either to a tempering furnace or across a cooling bed to a delivery conveyor. The mandrel and inside cooling head are then returned axially to the initial position to receive another heated tubular.